This trial will establish the safety of allogeneic mesenchymal stem cells (hMSC) infusion and determine their in vivo survival and distribution in a non-myeloablative setting. Results will allow us to design clinical trials using culture expanded hMSCs during alloegeneic stem cell transplantation with potential benefits of reduced engraftment failure and graft vs host disease (GVHD). In addition results will allow us to develop trials with gene transduced autologous hMSCs in the treatment of patients with genetic disorders and without suitable donors. The objectives are to: 1) determine whether hMSCs obtained from recipients of allogeneic bone marrow transplantation (allo-BMT) are donor or recipient derived. 2) determine the safety of allogeneic MSC infusion into patients who had previouisly undergone allogeneic bone marrow or stem cell transplantation with same donors' hematopoietic cells. 3) determine whether allogeneic culture expanded hMSCs can be detected in the host marrow following their intravenous infusion. 4) determine if donor MSCs contribute to correction of genetic disorder by assessment of disease specific clinical and laboratory corrolates.